The present invention relates to kiln furniture for holding ceramic products to be baked in high-speed backing kilns, and particularly, is directed to kiln furniture composed of a ceramic base material having a stack-up surface in contact with the conveyor or tunnel cars of the kiln and an emplacement surface for the ware. The kiln furniture can be advantageously used in different high-speed kilns where quite different conveyors, and even roller trains, are provided.
Most ceramic products, and especially fine ceramic products, such as procelain, are baked on or in kiln furniture at elevated temperatures. The baking takes place in baking apparatus, such as tunnel kilns, of different constructions. The kiln furniture, such as plates and pillars, are mounted in stories or layers on tunnel cars, the ware appearing in the individual stories, repeatedly stacked one upon the other. It is also known to use saggars having dimensions which are especially adapted to the dimensions of the ware.
Most conventional baking processes require long kiln cycles from cold to cold, even in the case of relatively short shift periods. Because of this, and together with the obvious disadvantage of the great energy requirement of such tunnel kilns, it is not possible or practical to automate the feeding and removel of ceramic products from the tunnel car, due to the multiplicity of ceramic products to be baked, and espcially due to the story-like mounting on the tunnel cars.
The kiln construction industry already has for a long time taken into account this situation and developed so-called high-speed baking kilns. Unlike traditional tunnel kilns, these high-speed kilns are not lined with heavy refractory materials of great heat-retaining capacity and very thick walls, but are essentially lined with ceramic fibrous materials. These novel refractory building materials, in fiber or wool form, have the advantages of high insulating capacity and therewith low energy consumption of the kiln, and low heat-retaining capacity and therewith low loss of energy when the kiln is started or brought to speed. Also, due to their fibrous structure, there is an extraordinarily high resistance to temperature change. These advantages of ceramic fibrous materials are utilized in high-speed backing kilns through which ceramic products pass in extremely short shift periods of time in a single layer, that is, not in the aforementioned story-like arrangement. However, these high-speed kilns, as a consequence of their specific advantages, must not be driven in a continuous operation, although they can be periodically switched on and off without great energy losses.
Exhaustive tests and research have shown that most ceramic products, especially fine ceramic products, can be baked per se without qaulity damage much more quickly than had formerly been possible. However, this has not been possible from a practical point of view, because the known kiln furniture is unable to cope with the hard operating conditions of high-speed kilns, particularly on account of insufficient resistance to temperature change. Despite considerable efforts, it has not hitherto been possible to improve the resistance to temperature change of already known kiln furniture, which are composed mainly of cordierite or silicon carbide. As a result, such known kiln furniture has not been economically employable in high-speed baking kilns.